Teen cannabis users face permanent IQ loss

August 28th, 2012

New results from a major international study spark fears that teen cannabis use causes brain damage and irreversible IQ loss in later life.

A team of international scientists have been monitoring the lives of 1,000 people in New Zealand for over 20 years in a bid to find out more about the long-term psychological effects of smoking cannabis from a young age.

The volunteers were assessed as children – before any had even tried cannabis, and then again repeatedly throughout their lives until the age of 38.

The researchers, writing in the US journal Proceedings of the National Academy of Sciences, found that: “Persistent cannabis use over 20 years was associated with neuropsychological decline, and greater decline was evident for more persistent users.”

Worryingly, those who persistently used cannabis (smoking it at least four times a week), suffered a significant decline in their IQ levels. Researchers also found that the greater the quantity of cannabis consumed, the greater the IQ loss.

Individuals who started smoking cannabis as adolescents experienced an average loss of eight IQ points, regardless of whether they gave up or cut down in later life. This suggests that the effects of cannabis use on teenagers are irreversible.

The new findings are consistent with previous speculations that cannabis permanently disrupts the wiring of adolescent brains going through critical development stages.

One member of the research team, Prof. Terrie Moffitt of King’s College London’s Institute of Psychiatry, has controversially concluded that although cannabis is risky for under-18s, it appears to be ‘safe’ for over-18s.

Cannabis is an illegal class B drug and is known to cause a number of physical problems, including lung and throat cancer, as well as extensive psychological problems.

Young people develop drug habits for a number of reasons, including:

escape from stresses and worries in life

peer pressure

need to experiment

boredom

enjoyment of the effects.

Some counsellors specialise in helping people overcome drug addictions. To find out more about how counsellors work and the services they offer, please visit our Types of Distress page.